The present invention relates to a method for making poly(arylene ether)-polyamide compositions.
Poly(arylene ether) resins are characterized by a unique combination of chemical, physical and electrical properties over a broad temperature range. This combination of properties renders poly(arylene ether)s suitable for a wide range of applications. However, the usefulness of poly(arylene ether) resins is limited as a consequence of their poor processability, impact resistance and chemical resistance. Poly(arylene ether)-polyamide compositions, as disclosed by Finholt (U.S. Pat. No. 3,379,792), overcame processability issues. However, the advantages of the Finholt invention are limited by the fact that when the concentration of the polyamide exceeds 20 weight percent (wt %), appreciable losses in other physical properties result. Specifically, there is no, or at best poor, compatibility between the poly(arylene ether) and the polyamide such that phase separation of the resin occurs on molding or the molded article is inferior in mechanical properties.
Compatibilized poly(arylene ether)-polyamide compositions have been produced utilizing a variety of base resins and compatibilizing systems. These thermoplastic products offer a wide range of beneficial properties which take advantage of the strengths of the basic resins while improving upon the weaknesses of each. Among the most useful properties of compatibilized poly(arylene ether)-polyamide compositions are excellent heat resistance, chemical resistance, impact strength, hydrolytic stability and dimensional stability. Such compatibilized poly(arylene ether)-polyamide compositions have found great utility in exterior automotive applications such as body panels. Examples of compatibilized poly(arylene ether)-polyamide compositions can be found in U.S. Pat. No. 4,315,086.
Polyfunctional compatibility modifiers can facilitate formation of a copolymer of the poly(arylene ether) and polyamide components. Such a reaction has been readily shown to take place under the time, temperature and shear conditions of typical thermoplastic extrusion processes. Copolymer produced in this fashion may serve as a melt surfactant which stabilizes the morphology of the resinous components of the system. Compatibility may also be achieved by improved interfacial adhesion of the resinous components.
Methods for making compatibilized poly(arylene ether)-polyamide compositions are well known in the prior art. U.S. Pat. No. 5,000,897 to Chambers, discloses a process for making a poly(arylene ether) and polyamide composition which is comprised of several steps. Poly(arylene ether) resin is blended with a first polyamide component together with a polyfunctional compatibility modifier, an optional rubber impact modifier and typical stabilizers, if desired. This mixture is fed to the feedthroat of an extruder which begins compounding the ingredients to provide an intermediate poly(arylene ether)-polyamide product. After the first compounding step, the second polyamide component is added to the intermediate poly(arylene ether)-polyamide composition, and additional compounding takes place. The compatibilized poly(arylene ether)-polyamide final product, which, in this instance, is the extrudate of the compounding process, is dried and pelletized by conventional means to provide thermoplastic resin products.
Poly(arylene ether)-polyamide compositions are usually amenable to many different types of processing operations, such as extrusion, compression molding and injection molding. However under certain conditions, final products resulting from the operations exhibit some imperfections. These imperfections fall into two classes, solid particles visible on the surface and flow disturbance artifacts such as pinholes, xe2x80x9cVxe2x80x9d shape imperfections, and sinkmarks visible as dents in the surface. These imperfections, which often become magnified when painted, are caused by carbonized particles (also known as pits) which are formed during processing operations such as extrusion and injection molding. Articles formed from poly(arylene ether)-polyamide compositions with surface imperfections are typically rejected, thereby increasing the manufacturing cost.
There is a continuing need to make poly(arylene ether)-polyamide compositions and articles from said composition with a decreased number of carbonized particles and a concurrently decreased number of surface imperfections.
A process to produce a poly(arylene ether)-polyamide composition, comprising creating and maintaining a substantially inert atmosphere in an extruder; combining poly(arylene ether) resin and an optional compatibility modifier in the extruder to form a mixture; compounding the mixture; and adding polyamide to the mixture and further compounding to form the poly(arylene ether)-polyamide composition.
Alternatively the process for producing a poly(arylene ether)-polyamide composition comprises creating and maintaining a substantially inert atmosphere in an extruder; combining poly(arylene ether) resin, an optional compatibility modifier, and up to about 20 wt % polyamide resin in the extruder to form a mixture; compounding the mixture; and adding additional polyamide resin to the compounded mixture and further compounding to form the poly(arylene ether)-polyamide composition.
Also part of the invention is a process for forming an article from a poly(arylene ether)-polyamide composition, comprising creating and maintaining an inert atmosphere in a molding device; adding the poly(arylene ether)-polyamide composition to the molding device; melting the poly(arylene ether)-polyamide composition; forcing the molten composition into a mold; and cooling the mold and releasing the resulting article.